Carrington Event in 1859 was last major solar storm to significantly impact Earth. At that time, no electrical grid existed, no solid state electronics were in use, no satellite navigation or comms systems existed, etc. So...our best indication of the likely effects comes from observed damage to telegraph wires that existed in 1859. In general, they were extensively damaged, resulting in multiple fires and lots of destroyed wiring. Specific effects on a localized basis will probably vary, but certain things are highly likely on a widespread basis: long transmission lines will induce very large voltage surges that damage transformers, effectively disabling our power grids. Imagine society without electricity, but also without the less sophisticated ways of getting things done that electrical appliances have displaced. No pumps to distribute water in urban centers, or to remove sewage. No heating for many homes. No refrigeration to keep perishable foods fresh. Urban centers quickly (within a week?) become untenable without electrical power.